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PenDataFromBuffer
2.0
Creates a HPENDATA object from serial data in a buffer. The buffer must have been previously
written by the PenDataToBuffer function.
LONG PenDataFromBuffer( LPHPENDATA lphpndt, UINT gmemFlags, LPBYTE lpBuffer, LONG cbBuf, LPDWORD lpdwState )
Parameters
lphpndt
Pointer to an uninitialized HPENDATA handle. If PenDataFromBuffer returns successfully, lphpndt points to a new HPENDATA object containing a copy of the serial points.
gmemFlags
Flag that specifies whether or not the Windows GlobalAlloc function should create a shared memory object when the pen data object is
created. This should be either 0 or GMEM_DDESHARE. The GMEM_MOVEABLE and
GMEM_ZEROINIT flags are added to this value and other GMEM_ flags are ignored.
lpBuffer
Pointer to a byte buffer containing serial data.
cbBuf
Size of the buffer, which must be at least 64 bytes in size. If the buffer
serves as an intermediate holding area, it need not be as large as the final HPENDATA object. To create the object, the application must call PenDataFromBuffer successively, each time reading a new section of data into the buffer that lpBuffer points to before the call. The example below illustrates this technique by
filling an HPENDATA object in stages, reading data from a file in cbBuf increments.
lpdwState
Address of a DWORD variable used by the system to maintain the transfer state.
The DWORD variable must be initialized to 0 before the first call to PenDataFromBuffer. Between successive calls to PenDataFromBuffer, the application must not alter the value that lpdwState points to. lpdwState can be NULL to signify that the buffer contains the entire data set for the HPENDATA object. This implies that subsequent calls to PenDataFromBuffer are not necessary.
Return Value
If successful, PenDataFromBuffer returns the number of bytes transferred from the buffer. If the size of the
pen data is larger than the buffer, the return value is equal to the buffer size
passed in cbBuf. A value of 0 indicates no more data to transfer. If there is an error, one
of the following negative values is returned:
Constant
| Description
| PDR_ERROR
| Parameter or overflow error.
| PDR_MEMERR
| Memory error.
|
Comments
The data being provided by the application must have been previously written
by the PenDataToBuffer function. The application cannot modify this data in any way. Embedded values
within the first 64 bytes provide information to PenDataFromBuffer about the size of the pen data.
PenDataFromBuffer creates an HPENDATA object and provides a handle to it. The application must destroy the object
when finished. The lphpndt argument points to a valid HPENDATA handle only if the function returns PDR_OK.
While this function is reconstituting the HPENDATA object, the application must not attempt to use it in any way because it will
be invalid until the last buffer is read.
Example
The following example shows how to create a HPENDATA object from a file (hfile) that has already been opened for reading. Before reading the pen data, its
length is retrieved from the file:
#define cbBufMax 1024
HPENDATA NEAR PASCAL ReadPenData( HFILE hfile )
{
HPENDATA hpndt = NULL;
LONG cb, cbRead, cbHpndt;
BYTE lpbBuf[cbBufMax]; // Buffer
DWORD dwState = 0L; // Must initialize to 0
if (!hfile
|| (cb = _lread(hfile, &cbHpndt, sizeof(DWORD))) == HFILE_ERROR
|| cb != sizeof(LONG))
return NULL;
while (cbHpndt > 0)
{
if ((cbRead = _lread( hfile, lpbBuf, min(cbHpndt, cbBufMax )))
== HFILE_ERROR
|| PenDataFromBuffer( &hpndt, 0, lpbBuf,
cbBufMax, &dwState ) < 0)
{
if (hpndt)
DestroyPenData( hpndt );
return NULL;
}
cbHpndt -= cbRead;
}
return hpndt;
}
See Also
PenDataToBuffer, GetPenDataAttributes
Related Links
Software for Delphi and C++ Builder developers
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